Fuel cell stacks operate at relatively high voltage levels and higher temperatures. The fuel cell system includes a high voltage direct current (HVDC) bus that provides power from the fuel cell stacks to a load. The HVDC bus is subject to electromagnetic interference (EMI), which detrimentally effects the performance of the fuel cell system. Y-capacitors (Y-caps) are incorporated to protect the HVDC bus from EMI. The Y-caps bridge the positive and/or negative DC to chassis or safety ground.
In the event of a fault contact, the Y-caps discharge through the resistance of the fault contact. For example, when a person touches either the positive or negative nodes of the HVDC bus and chassis or safety ground, the Y-caps discharge through the body of the person. As a result, the capacitance of the Y-caps must be limited to ensure that the energy released in the event of a fault contact is within safe limits. Because the Y-caps are limited, the ability to protect against EMI is correspondingly limited.